Control system



May 278, 1935. s. c. HENTON Er AL 2,003,047

CONTROL SYSTEM Filed June 9, 1932 4 Sheets-Sheet l 'EHA l /Ob .9b

ATTORN w'lTNEssEs:

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May 28, 1935! s. c. HENTON ET AL- l 2,003,047

CONTROL SYSTEM Filed June 9. 1932 n 4 Sheets-Sheet 2 ATTOR Y May 28, 1935. sfc. HENTON ET A1,.. 2,003,047

CONTROL SYSTEM Filed June 9, 1932 4 Sheets-Sheet 3 ATTORN May 28, 1935 s. c. HENTON ET Al. 2,003,047 `CONTROL SYSTEM iFiled June 9, 1932 4 sheets-sheet 1 a ATTORN Patented May 28, 19035 UNITED STATES PATENT OFFICE CONTROL SYSTEM Stuart C. Henton', Akron, and Melville B. Rankin, Cuyahoga Falls, Ohio Our invention relates, generally, to electrical control systems and it has particular relation to systems for controlling and supervising the operation of electric circuit breakers located at a remote point.

Inthe past, when it hasbeen desired to control the operation of a linnted number `ofcircuit breakers or otherV apparatuslunits, located at a point lremote from the control station or oiiice where an operator is located, it has been necessary in most instances to use one of the various kinds of supervisorygcontrol systems for effecting the continuous supervision and control of the circuit breakers. These systems are, as a general rule quite complicated and expensive to install and maintain in eiiicient operating condition. Consequently, the expense involved in using such a system is prohibitive in many instances where it is necessary to reduce operating and installation costs to a minimum.

If the usual supervisory control systems are not used, it has been necessary to use expensive polarized relays or to use several conductors between the oilice and the remote point for controlling and supervising each circuit breaker or apparatus unit.

All of these systems have the very serious objection that they are expensive to install, either because of the comparatively large quantity of complicated apparatus necessary for their successful operation, or because of the large number of conductors which must be run between the control oiiice and the sub-station for eiecting the desired control and supervision of the apparatusunits. Y

It is, therefore, an object of our invention to provide a remote control system which shall be simple and efficient in operation and which may be readily and economically manufactured and installed.

It is also an object of our invention to provide for controlling the operation of a circuit breaker or other apparatus unit at a remote point by applying different polarities to a single control conductor.

A more specic object of our invention is to provide for controlling and continuously supervising the operation of a circuit breaker located at a remote point over a single control conductor.

A nother object of our invention is to provide for automatically transferring a main power bus from one source of supply to another in the event that one of the sources of supply should fail.

Still another object of our invention is to provide for controlling, over a pair of conductors, the operation and supervision of remotely located circuit breakers which are arranged to automatically transfer a power bus from one source of supply to another in the event that one of the 5 sources of supply should fail.Y

Another object of om' invention is the provision of a system of the above character which operates on ropposite polarities Without the use of polarized relays the operation oi which is un- 10 ai'iected inthe event of a single incidental ground at any point on the system or in the event of the reversal of polarity on common direct current supply bus.

Other objects of our invention will, in part be obvious and will, in. part appear hereinafter.

The invention, accordingly is disclosed in the embodiment thereof shown in the accompanying drawings and comprises the combination of elements and arrangement of parts that will be exemplied in the embodiment hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawings in which:

Figure l is a diagrammatic View of a remote control system showing a plurality of circuit breakers each of which may be controlled and supervised at a distance over a single control conductor.

2 is a diagrammatic view of a remote control system showing a preferred and an auxiliary circuit breaker, together with suitable control apparatus for automatically transferring a main power bus from one source of supply to another in the event that one ci" the sources of supply should fail, and 40 Figs 3 and 4 are modifications of the system shown in Fig. 2.

Fig. 5 illustrates, in detail, the construction of the position indicators which may be used for indicating the condition of the circuit breakers.

In order to effect the control and supervision of remotely disposed circuit breakers according to this invention, it is only necessary to provide a commondirect-current control Tous connecting the sub-station and the cnice and to supply a single control conductor for each circuit breaker which it is desired to control and supervise.Y

In order to close a circuit breaker at the substation, a negativeV potential is applied to the con- 55 trol conductor by means of a suitable control switch, which causes a circuit breaker closing relay to be energized through a closed auxiliary contact on the circuit breaker. The breaker closing relay causes the closing coil of the circuitA breaker to be energized which, in turn, op-

erates the circuit breaker to the closed position, n

and, at the same time, opens the circuit for the breaker closing relay and closes a second circuit in series with the trip coil of the circuit breaker to the control conductor.

In order to indicate the position to which the circuit breaker has been operated, an operation indicator is provided which comprises two windings that are connected together at one end and to the control conductor, the other ends of which are, respectively, connected to the positive and negative control buses. When either of the windings is energized, a color indicator is moved in accordance with the coil which has been energized to indicate' the last operation of theY breaker. The resistance of the coils ofthe indicator is relatively high and therefore, they require only a very small amount of'currentfor operation. 1 'Y When a negative potential is applied to the trip coil on closure of the circuit breaker, the negative potential is also applied to the control conductor. The coil inthe position indicator, which is connected to the positive control bus, will then be energized and the corresponding indication of the last operation of the circuit breaker willbe obtained. VIt should be noted, however, that while suiiicient current is caused to iiow through the indicator to perform the desired indicating operation, this current is not suilciently large to cause the trip coil to be energized to such an extent as to trip the closed breaker.

When it is desired to open the circuit breaker, it is only necessary to apply a positive potential to the control conductor through the operation. of a suitable control switch which energizes the trip coil through auxiliary contact members on the circuit breaker.

When the breaker opens positive potentialis applied to the control conductor which willcause the coil in the position indicator that is con- V nected to the negative bus at the oice to be energized, thereby operating the indicator to show that the circuit breaker has been opened.

ln order to prevent a pumping action on the part or a circuit breaker in the event that it is closed on a fault, a relay system `is provided whereby theclosing mechanism for the circuit breaker cannot be energized more than once for V a single operation oi the closing control switch. The relay system is arranged to open the control conductor in the event or a fault to necessitate the return of the close control switch to the ofi position before a subsequent-closing operation can beperiormed.

For a more detailed description of the operation of the above-described system, reference may be had tovFig. i the numeral i indicates a plurality of circuit breakers which arefto be controlled in accordance with this invention. As shown infthis gure, several circuit breakers may be connected to a common power bus and may be arranged to supply power to any circuits, as may be desired through conductors 2. VSince the control circuits and equipment may be in duplicate for each circuit, the same numerals and description willbe applicable to each'of the circuit breakers shown. t will also be apparent that as many units may of the drawings, in which,

be added as required merely by increasing the number of control units.

In order to supply suitable control current for operating the system, positive and negative control buses comprising conductors 3 at the substation and Il at the oiice are connected to suitable sources oi direct-current. These control buses are connected together by means of conductorswhich extend as indicated from the ofce to the sub-station and thus provide a common direct-current control bus. Y 1 The only other Vconductors which connect the oiiice with the sub-station are the single control conductors 5, each of which is associated at the office end with its particular control equipment and at the sub-'station end with a circuit breaker and its associated control equipment.

With a View to obviating the necessity for supplying the energizing currents for the closing coils of the circuit breakers over the control conductors Ei,v auxiliary relays l are provided which are so-constructed as to hold their contact members 8 closed for 4an appreciable time after their operating coils have been de-energized. Y

Closing and tripping operations of the circuit breakersrmayrbe effected from the oiiceend by means of suitable control switches 9 and I, respectively, which are operable Vto connect the controlconductors 6 either to the positive or the negative control busde'pending on whether it is desired to open or close Va' circuit breaker. VVAs illustrated, the control switches are of Vthe pushbutton type having normally closed contact members 9a and Ea and normally open contact mem- -bers Sib and lb, respectively..

Itis to be understood, however, that any other suitable type control switch may be used or. a single switch may be used which may be operated to one position to close a breaker and to another position to open the breaker and having a normally closed operating position thereby performing Vthe same function as the normally closed contact members Sa and lila illustrated. Y

The position of, theA circuit breakers is indicatedat the oce or at any other point by means of position indicators il each of which is provided with two operating windings l2 and I3. As shown, winding I2 is connected Vbetween the positive control bus and the control conductor 6 while winding i3 is connected between the negative control bus and the control conductor 6. Consequently when a positive potential is impressed upon the control conductor 6, the winding I3 isenergized and operates the indicator to one position while if the control conductor 6 is energized with a negative potential the winding l2 is energized to'operate the indicator to a differenty position.

As shown, two complete oice control stations are provided each comprising'a close switch 9, a trip switch lil and a' position indicatorV il although it is to be understood that only one control station may be used or as many as is desired, since the operation Aof any switch 9 will close the circuit breaker associated therewith or the operation of any switch le, will open it.

When it is desired to close a circuit breaker it is only `necessary to depress the closing switch 9, thereby applying a negative potential to the control conductor 6 and causing the energization of the circuit breakerrrelay l, over a circuit which may be traced 'from energized conductor l5,V through the actuating coil of relay 1, conductor I4, auxiliary contact membersV i5 of the circuit breaker I and through conductor I6 to the positive side of the control bus 3. The energization of relay 'I causes contact member 8 to be bridged, thereby completing an obvious energizing circuit for the closing coil I l of the circuit breaker.

The closing of the circuit breaker I causes its contact members I5 to be opened and Contact members i8, to be closed, thereby applying a negative potential from the control bus 3 through conductor I9, contact members I3, conductor 2B, trip coil 2l of the circuit breaker I, conductor 22 tc the control conductor 6. When the control switch 9 is released, a circuit is completed from the energized control conductor 6, through contact members 9a and lila and coil I2 of the posi` tion indicators at each station to the positive bus thereby operating the indicators II to show that the breaker has been closed.

When it is desired to open the circuit breaker I, the trip switch IG is operated, thereby energizing the trip coil 2I over a circuit which may be traced from the positive side of the control bus 4 to the control wire 6 and through conductor 22 to the trip coil 2l of the circuit breaker I, thence through conductor 2i), contact members IS, and conductor I to the negative side of the control bus 3. The circuit breaker I is then opened and the contact members I5 located thereon, are bridged, thereby applying positive potential from the positive side of the control bus 3 through conductor I6, contact members I5, conductor I4, winding of relay l', control conductor 6 to the coils I3 of the position indicators II through the normally closed contact members 9a and Illa of the control switches. The positive potential thus applied to the windings i3 of the position indicators causes them to be operated to indicate that the circuit breaker l has opened.

Since the position indicators II require but a small amount oi current for their operation, it will be observed that several of these indicators may be applied, where desired, at various points along the control system. As shown, a position indicator is also provided at the sub-station in addition to the two at the control end in order that an attendant may ascertain the position of the circuit breaker without actually inspecting it.

As many circuit breakers as are desired may be added at the sub-station. For each additional circuit breaker, it will only be necessary to supply one additional conductor between the circuit breaker and the oiiice for eilecting both the control and the supervision since the conductors 5 serve to connect the control buses for any number of circuit breakers.

In the event that it is desired to provide for preventing more than a single operation of one of the circuit breakers when the close control switch associated therewith is operated, the trip free relay system, shown generally at 23, may be employed. While the relay system 23 is shown in connection with the middle circuit breaker control unit, it will be readily understood that it may be used in conjunction with either of the other units shown or in conjunction with the systems which will be described hereinafter.

The relay system 23 may comprise a current overload protective relay 2li whose contact members 25 are closed when a predetermined current flows in the conductors 2. In addition to the protective relay 24, a control relay 2B and a lockout relay 2'I are also provided.

The only change involved over the control system described hereinbefore is the connecting of the control conductor through the normally closed contact members 28 of the relay 26. Under normal operating conditions, the functioning of the control unit with the relay system 23 applied thereto is the same as described above. However, in the event that there is a fault on the conductors 2, the operation will be different and it is described as follows:

Referring now particularly to the middle circuit breaker control unit of Fig. .l and assuming that negative potential has been applied to the control conductor i by the operation of the close control switch 9, the relay 'I will be energized, as herein-l beiore set forth, through the closed contact members 28 of the control relay 26, thereby energizing the closing coil I'I and closing the circuit breaker I.

If there is a fault on the conductors 2, the current overload relay 24 will be energized suiliciently to cause its contact members 25 to close. The energization of relay 24 will complete a circuit for energizing relay 26 which may be traced from the negative side of the control bus 3, winding of relay 26, contact members 25 of relay 24 and conductor 29 to the positive side of the control bus 3.

The energize-tion of relay 26 opens the control conductor 6 at the contact members 2S and completes a circuit for immediately tripping the circuit breaker I. It also completes a circuit for energizing the lock-out relay 2l' and for holding itself closed until the control switch 9 is released.

The circuit for tripping the circuit breaker I may be traced from the positive side of the control bus 3, through closed contact members of relay 26, conductor 22, trip coil ZI, conductor 23, contact members I3 and conductor i9 to the negative side of the control bus 3.

The circuit for energizing the lockout relay E? may be traced from the negatively energized control conductor S, through contact members 3i of relay 2S, and winding of relay i'l the positive side of the control bus 3.

The energization of relay 2l completes a circuit for holding energized the control relay 2B which may be tr ced from the positive side of the control bus 3 through contact members of relay 21 and contact members 33 of relay 28, and winding of relay E to the negative side of the control bus 3.

As long as the control switch S remains closed, the relays 2E and 2 will remain energized and no further operation of the circuit breaker I can take place until the control switch 9 is released and again closed.

When it is desired to insure that power will be supplied to a customer, is the usual practice to provide for supplying the power not only from a single preferred feeder' circuit but also from a second or auxiliary feeder circuit. It is then desirable to provide for automatically transferring the customer from the preferred circuit to the auxiliary circuit in the "vent that the power supply should fail on the former circuit. At such time when the power is applied. to the preferred circuit vit is desirable to transfer the load back to this circuit automatically.

In a system of this type, provision is made for indicating to an operator at a central control point or oflice which circuit is supplying power to a customer and, further, provision is made to enable him to control either of the supply circuits so that he may parallel them in some cases, or so that he may cause the auxiliary circuit to be continually the source of power for the customer rather than the preferred circuit.

CTI

According to this invention. we haverprovided for securing these desired results by the provision of the remote control systemshown in Fig. 2.

This system comprises a main power bus which may be fed either from a preferred feeder circuit 35 orA from an auxiliary feeder circuit 3l. The preferred'feeder circuit 36 is connected to the main power bus 35 through conductors 4i! and il of the control bus at the substation and conductors 5 and E at `the oflice by means of conductors i9 and l and control a preferred circuit breaker P, while the auxiliary feeder circuit 3l is connected to the main power bus 35 by means of an auxiliary circuit breaker A.

The preferred circuit breaker P is provided with a trip coil 33 which is disposed to be energized directly from the control circuit and a closing coil Sil which is disposed to be energized from a control bus, comprising conductors Il@ and 4l,

upon the operation of a circuit breaker closing relayv d2. In like manner the auxiliary circuit breaker A is provided with a trip coil i3 and a closing coil which is disposed to be energized on operation of a circuit breaker closing relay 65.

VThe circuit breaker closing relays d2 and l5 areV Y tive circuit breakers P and AV have closed.

In the event that the power supply to the preferred feeder circuit S5 should fail, an actuating l relay 45, which has previously been energized on the operation of a voltage delay relay lil, is deenergized thereby causing a transfer relay d8 to be energized. The energization of relay i3 simultaneously causes breaker P to be tripped and circuits to be completed which result in the operation cf the auxiliaryv circuit breaker A to the closed position.

The circuit breakers P and A may be controlled and supervised from the office by the operator in the manner set forth hereinbefore in connection with Fig. l. As described hereinbefore, as many control points may be provided as are desired by the addition of the necessary number of close and trip switches Eli and it, respectively. In like manner additional position indicators il may also be provided. Suitable connections are made between the office and the circuit breakers byrmeans of conductor El provided for each circuit breaker.

With a view to preventing the automatic operation of the transfer relay d3, at thewill of the operator, locking relays 52 and 53 are provided. It will be observed when relay d8 is de-energized, that lock-in coil EQ of relay 52 is connected in shunt-circuit relation with the actuating coil of relay i2 while the lock-out coil 55 of relay 52 is connected in shunt-circuit relation with the Vtrip coil Sii of circuit breaker P. It will also be observed, when relay 58 is cle-energized, that the lock-in coil .5S of relay 53 is connected in shunt circuit relation with the trip coil 43 of the auxilf iary circuit breaker A while Ythe lock-out coil 5l of relay 53 is connectedin shunt-circuit relation with the actuating coil of relay 45.

When the operator at the office causes the circuit breaker P to be tripped, the lock-out coil 55 of relay 52 will be energized therebf,7 hreventing the energization of relay d8 and the subsequent automatic operation of the auxiliary circuit breaker A. In like manner, when the operator at the office causes the auxiliary circuit breaker A to be operated, the lock-out coil 57 of relay 53 is energized thereby preventing the automatic transfer to the preferred circuit. In order' to restore the system for automatic operation, it isV necessary for the operator to open the auxiliary circuit breaker A and to close the preferred circuit breaker P. The system will then be so arranged as to automatically'transfer from the preferred feeder circuit 3S to the auxiliary feeder circuit 31 when the power is lost on the former and to automaticallyV return to the preferred circuit on return of power thereto.

Thevoltage delay relay il is of the type which is disposed to operate to bridge its contacts a predetermined length of time after power has been applied tothe preferred feeder circuit 36. This time delay is .desirable in order to insure that the power has been definitely returned"v to the preferred circuit. The danger of initiating the automatic operation of the system back to the preferred feeder circuit on a return of power thereto for a very short period of time is thus eliminated.

In order to protect the system in the event that a fault should occur, current overload relays 58' and 59 are provided which may beof Yany well known type Vsuitable for this purpose and are disposed to be connected Vto the feeder circuits 3'3 and 3l, respectively, by means of current transformers Si and t2.

In order to prevent an automatic transfer to l the auxiliary feeder circuit El should it not be ener `ized when power is lost on the preferred cir cuit an under-Voltage relay S3 is provided. This relay is provided with contact members connected in the energizing circuit for the transfer relay d8 which are closed when power is applied to the auxiliary circuit to render the transfer relay [iii operable and are open when the auxiliary circuit is deenergized thereby preventing operation of the transfer'relay 48.

With a view to more fully describing Vthe nature of the remote control and automatic changeover system shown in Fig. 2 of the drawings; a detailed description of its function and operation will be given.` It will be assumed that power is applied to both the preferred feeder circuit 3S and to the auxiliary feeder circuit 3l. It will also be assumedv that the lock-in coil 56 of the locking relay 53 has been energized by some previous operation so that the contact members 5d of this f preferred feeder circuit at the control station is depressed by the operator, a negative potential is applied from the control bus conductor Q, con- ,ductorr 5.25, through contact members 66 of the transfer relay d8, conductor 6l, lower Contact members @t of overload relay 5t, conductor 69, the actuating coil of the circuit breaker-closing relay d2, conductors i and l'i, and auxiliary contact members 22 on the preferred circuit breaker P to the positive control bus. The circuit breaker-J closing relay l2 will then be energized and in turn the closing coil 39 of the preferred circuit breaker P will be energized over an obvious circuit, tnereby causing the circuit breaker P to be actuated to the closed position.

At the same time that the actuating coil of the relay i2 is energized it will be observed that the lock-in coil 5ft of relay 52 is also energized since it is in shunt circuit relation with lthis coil as hereinbefore set forth. The energization of the lock-in coil 54 insures that contact members l2 of the locking relay 52 will be closed so that the system will be arranged or set up for automatic change-over operation.

Upon closure of the circuit breaker P, auxiliary contact members 25 of the circuit breaker will be bridged, thereby applying negative potential from the control bus to the trip coil 38 of this circuit breaker and back over the circuit previously traced, in connection with the energization of the actuating coil of relay 42, to the operation indicator .l1 at the office where the coil I 8 of the indicator will be energized, thereby indicating to the operator that the circuit breaker P is now in the closed position.

If for some reason the power fails on the preferred feeder circuit 36, the voltage-delay relay 41 and the actuating relay 45 Will immediately become de-energized. A circuit will then be set up for energizing the transfer relay 48 which may be traced from the negative control bus through the bridged contact members 13 of the circuit breaker P, conductor 14, Contact members 15 of the actuating relay 46, conductor 11, contact members 12, the operating coil of relay 48, contact members 64 of relay 53, conductor 18, bridged contact members 19 of the under-voltage relay E3, conductor 88, contact members 8l, conductor 82 and bridged contact members 22 of circuit breaker A to the positive control bus.

The ltransfer relay 48 is thus energized and operates to complete a trip circuit for the preferred circuit breaker P which may be traced from the negative control bus through bridged contact members 25 on the circuit breaker P, trip coil 38, conductor 68, contact members 68, conductor 61, contact members 83 of transfer relay 43, conductors 84 and 18, contact members 18, conductor 88, contact members 8|, conductor 82, and contact members 22 of the auxiliary breaker A to the positive side of the control bus.

At the same time the operation of the transfer relay 48 effects the energization of the control relay 45 for auxiliary breaker A over a circuit which may be traced from the positive control bus, contact 85 of the auxiliary circuit breaker A, conductor 86, actuating coil of relay 45, conductor 8i, contact members 88 of over-load relay 59, conductor 89, contact members 9U of the transfer relay 48, conductor 11, contact members 15, conductor 14 and contact members 13 on the preferred circuit breaker P to the negative control bus. The closing coil 44, of the auxiliary circuit breaker A, will then be energized with the result that this circuit breaker will be closed.

As soon as the circuit breaker P has been tripped, contact members 13 will be opened with the result that the transfer relay 48 will be deenergized. A circuit will then be established for transmitting the indication of the position of the auxiliary circuit breaker A to the oflice by means of a circuit which may be traced from the negative bus through contact members 25 on the auxiliary circuit breaker A, trip coil 43, conductor 81., contact members 88, conductor 89, contact members 9| of transfer relay 48, conductor 92, conductor 9, control switches l5 and I6, and coil I8 oi` position-indicator l1 to the positive control bus, thereby indicating that the auxiliary circuit breaker A has been operated to the closed position` In the event that power is again applied to the preferred feeder circuit 36 the voltage-delay relay 41 will be energized and after a predetermined length of time its contact members will close to complete an obvious circuit for energizing the actuating relay 46. The transfer relay 48 will conductor 96 and contact members 9? of the auxiliary circuit breaker A to the negative side of the control bus. The trip coil of circuit breaker A will then be energized over a circuit which may be traced from the negative side of the control bue, contact members 25 of the auxiliary circuit breaker A, trip coil 43, conductor 81, Contact members 88, conductor 89, contact members 9G, conductor 11, contact members 94, conductor 93 and contact members 82 to the positive side of the control bus.

At the same time the circuit breaker relay 42 will be energized over a circuit which has been traced hereinbefore.

Suitable indications will be given back to the eflice over circuits which have been traced hereinbefore.

In the event that the operator wishes to parallel the preferred circuit 36 With the auxiliary feeder circuit 31, the control switch l5 that is associated with the auxiliary breaker is depressed thereby causing the energization of relay 45 over a circuit which may be traced from the negative control bus at the office, conductors 9 and 92, contact members 9|, conductor 89, contact members 88, conductor 81, actuating coil of relay 45, conductor 86, and contact members 85 to the positive side of the control bus. The auxiliary circuit breaker A will then be actuated to the closed position as hereinbefore described.

At the same time that the actuating coil of relay 45 is energized the lock-out coil 51, of the locking relay 5S, is also energized over a circuit which extends from the energized conductor 9, through the lock-out coil 51, conductor 86, and contact members 35 to the positive control bus. Automatic change-over operation of the system will then be precluded until such time as the operator depresses the control switch I8 associated with the auxiliary circuit breaker A to actuate this circuit breaker to the open position.

In the event that an overload occurs on the preferred feeder circuit 3E, the over-load relay 58 will be actuated and contact members S8 on this relay will be closed to establish a trip circuit for circuit breaker P which extends from the positive side of the control bus, Contact members 98, conductor S9, trip coil 38, contact members 25 to the negative side of the control bus. The circuit breaker P will then be automatically opened, but since power is still applied to the preferred circuit and relays 46 and 41 are energized, no automatic transfer to the auxiliary feeder Vcircuit will take place. In like manner, if power is being supplied over the auxiliary feeder circuit, the current overload relay 59 will serve to trip out the circuit breaker A in the event of an overload.

In order to insure that either the auxiliary circuit breaker A or the preferred circuit breaker P has been tripped prior to the closing of the other breaker, the system shown in Fig. 3 may be utilized. This system is identical with that shown in Fig. 2 with the exception that an interlocking relay 180 is added together with certain changes in the circuits by mea-ns of which automatic operation is effected. In addition, the

transfer relay 48 is arranged so as to remain in `the energized position for a short interval of time after its actuating coil has been de-energized. Briefly, thefunction of the interlocking relay IES is to connect the trip coil of either circuit Vbreaker directly to the positive potential rather than to necessitate the circuit being completed through the auxiliary contacts on the other circuit breaker. The actuating coil of relay i is connected in parallelcircuit relation With the actuating coil of relay e5 and isk disposed to be energized in responseY to the operation of the under-'voltage relay 4l.

In describing the function of the interlocking relay i638, it will be assumed that the system has been operating with the preferred circuit breaker P closed and supplying power to the main power bus from the preferred feeder circuit 35. It will also be assumed that contact members 'l2 and 6A on relays 52 and` E3, respectively, are closed and that the voltage relay t3 is energized from the auxiliary feeder circuit 3l.

In the event of a power failure on the preferred feeder circuit 36, relays et, il and IBS will be de-energized immediately. VAs a result of the d-e-energization of relay 18, the transfer relay 48 will be energized over a circuit which may be traced from the positive control bus through con tact members 'IS of the preferred circuit breaker P, conductor lll, contact members l5, conductor IGI, contact members l2, actuating coil of relay 48, contact members 6d, conductor 02, contact members 19, conductor 8S, contact members 8|,

,conductor 82 and contact members 22 to the neglay I, to the positive side of the control bus.'

In response to the opening of the preferred circuit breaker P a circuit will be, completed for energizing the closing relay d5 to effect the closing of the auxiliary circuit breaker A.

The circuit for energizing relay 45 Vmay be traced from the positive control bus, contact members 35 of the auxiliary circuit breaker A, conductor 8B, actuating coil of relay 55, conductor 81, Contact members 88, conductor te, contact members 90 of the transfer relay Q8, conductor |05, contact vmembers it, conductors lill and S3 and contact members S2- which are closed when the preferred circuit breaker P is open, to the negative-control bus.

It Will be observed that .the circuit for closing the auxiliary circuit breaker A is not completed until the preferred circuit breaker P has been' opened and contact members 92 on this circuit breaker have been bridged.

The usual indications for showing that the preferred circuit breaker P has been opened and the .auxiliary 'circuit breaker A has been closed will be transmitted back over the respective control circuits to the operation indicators l l at the oflice, as hereinbefore described, The transfer relay .ll'will also be de-energized because of the opening of contact members "13 of the preferred circuit breaker P. Y

In the event that power returns to the preferred feeder circuit 36, the main power bus will' be automatically transferred from the auxiliary feeder circuit 3l back to the preferred feeder circuitr'. A predetermined time after power has been returned to the preferred feeder circuit 36, the voltage delay relay il will be actuated to its closed position thereby energizing the actuating contact members 12, conductor 1.6i, contact mem-A bers ed, conductor 93 and contact'members S2 of the preferredv circuit breaker P, to the negative control bus. l y

The closing of ytransfer relay Z8 establishes a circuit for tripping the auxiliary circuit breaker A Which may be traced from the negative control/f bus, through contact members 5 of the auxiliary circuit breaker A, trip coil lit, conductor 8l, contact members 8S, conductor et, contact mem.- Vbers Si), conductor E95, and contact members Hi8 of the interlocking relay 09 to the positive control bus;

When the circuit breaker A is tripped, a circuit is established for energizing the closing relay 42 associated with circuit breaker P, which may be traced from the positive control bus, contact members 22'of the preferred circuit breaker P,

actuating coil of relay 42, conductor 69, contact members et and-83, conductor 93, contact members 99 of the Vinterlocking relay itt, conductors 10B and 82, and contact members of circuit breaker A to the negative control bus. Y It Will be again observed that it is necessary for the auxiliary circuit breaker A to be in the open position and for itsY contact members ZZ to be bridged before the preferred circuit breaker P may be closed. Y Y

Referring now to Fig. 4 of the drawings, the electrical control system shown is especially adapted for automatic operation of the transfer feeder system'in which it is desired to Varrest the operation of the automatic transfer system and to operate both feeder circuits in parallel.

In general, this system comprises, at the oice, closing switches l5 and trip switches it together with 'operation indicators il associated with the preferred and auxiliary feeder circuits as described hereinbefo-re, In addition, the control bus, comprising the positive and negative conductors 5 and 6, is provided at the office and is connected to the lcorresponding control' bus at the sub-station by means of conductors 49 and 50. In addition, control conductors 9 are provided for connecting the control apparatus associated with each individual` circuit at the oilce and at the sub-station. Y

At the sub-station, a preferred circuit breaker Plis Yprovided having a trip coil 38 and a closing coil 39. In order to actuate the circuit breaker P to the closed position, a circuit Vbreaker closing relay i2 is provided. An auxiliary circuit breaker A isY also provided at the sub-station having a trip coilfi and a closing coiled together with a circuitbreaker closing relay 45, v

,It will be observed that the preferred circuit breaker P is disposed to connect the main power bus 35 to the preferred feeder circuit 3e while the auxiliary circuit breaker A is disposed toY connect the main power bus 35 to the auxiliary feeder circuit 31. l

In order to render the system automatically responsive to the voltage applied to theY preferred feeder circuit 36, the under voltage relay Slis provided, the contact `members of which are disposed tc be bridged a predetermined length lof time after voltage has been applied to its ractuating coil. The bridging of the contact members of relay V`4'I effects the energization of the coil of the actuating relay 5S, the function lof which will be set forth hereinafter.

The manual operation of the circuit breakers may be effected by means of main control relays and 'I I2 which serve to energize the doublecoil lock yout relays H3 and II. The operation of the lockout relays H3 and ||4 serves to energize a transfer relay IIS, `the function lof which will be vset forth hereinafter.

In the event that it is desired to arrest the automatic operation of the system when the auxiliary circuit breaker A is closed and to prevent the preferred circuit breaker P from closing on return of power to the preferred circuit 35, Van automatic arresting relay I IS is provided which may be actuated by means of a push-button svvitch ||`I l0- cated 'at the oice.

`In vorder to more clearly set forth the operation of this system, the operation necessary to cause the closing and tripping of the auxiliary circuit breaker A will be described. It will be assumed that power is applied to both the preferred feeder circuit 36 and the auxiliary feeder circuit 3l and that both preferred circuit breaker P and the auxiliary circuit breaker Aare open.

The operator now depresses the close switch |57, associated with the auxiliary circuit at the oiiice, and thereby applies negative potential from the control bus 5 through conductor 9 to the actuating coil of the relay H2 through conduotor H8, contact members HS of the auxiliary circuit breaker A to the positive control bus. The main control relay |I'2 is then closed to energize the right-hand coil of lockout relay H4 over a ircuit which may be traced from the positive control bus, contact members ||9 of the auxiliary circuit breaker A, conductors H8 and |29, contact member lili of the arresting relay H6, conductor |22, contact members I'i and S24 of the main control relay IIZ, conductor |25, and actuating coil |25, to the negative control bus. The right-hand contacts |28 of relay ||4 will then be closed. However, no further operation will be accomplished until the operator-releases the close switch I5. v

When the operator releases the close switch i5, relay I |2 is de-energized and opened to cornplete a circuit for energizing the circuit breaker closing relay 5 which may be traced from the positive control bus, through contact members |29 of the auxiliary circuit breaker A, actuating coil of relay 45, conductor |39, contact members I3| of relay H2, conductor 'il-l2, contact members |33 of relay l l5, conductor i313 and contact members I 28 to the negative control bus. The contact members |45 of relay 45 are thus closed to energize the closing coil d ci the auxiliary circuit brea er A over an obvious circuit.

The indication, that the auxiliary circuit breaker A has closed, will be transmitted to cnice from the sub-station over a circuit whic. may be traced from the negative control bus, through contact members |35 of the auxiliary circuit breaker A, conductor |58, actuating coil of relay I'2, conductor 9 and coil I8 of operation inductor Il, to the positive control bus. The energization oi coil I8 operates the indicator Il to show that the auxiliary circuit breaker A has been closed.

In order to open the auxiliary circuit breaker A, after it has once been closed, the operator depresses the trip switch l that is associated with the auxiliary circuit bre^l=er A at office and applies positive potential from the control bus to the conductor S and through the operating coil of relay i i2, conduct i i8 and contact inembers |35 of the auxiliary circuit breaker A, to the negative control bus at sub-station.

Relay I I2 is thus energized and closes, to establish a circuit for energizing the lett-'nood coil 98 of relay H4 which may be traced irom the negative control bus, through contact rlembers |35 ofthe auxiliary circuit bre ker A, conductors H8 and |2, contact members 52| of relay H5, conductor |22, cont ct members E23 and of relay I I2, conductor t3?, and actua ng coil l8r? to the positive control The lei and contact members of relay i l en closed through the energization of the lag-hand actuating coil |99.V However, no further action t Tres place until the operator releases the it has returned to the r.

l the A circuit is then completed for tripp g the auxiliary circuit breaker A which may be traced from the negative control Tous, t rough contact members 38 of the auxiliary circuit breaker A, trip coil 43, conductor contact members itl, which are bridged when relay l is fle-energized because of the release oi the trip switch ill, conducto-r |32, contact members 32, conductor 34, and contact members i3@ of relay Hit, to the positive control The auxiliary circuit breaker A is then opened and the corresponding indication is shown on the indicator il associated with the auxiliary circuit breaker at the ofce in the same manner as heretofore described in connection with the closing ci this circuit breaker.

In order to close the prefered ci. cuit 1:reaker and to set up the system for automatic operation alter the auxiliary circuit breaker has been tripped, manually, as previously c oribed, the operator closes one of the close switches l5 associated with the preferred circuit breaker at the oflice. The closure of the switch l5 applies negative potential from the control Tous 5 to conductor 9 and the actuating coil oi control relay I I I through conductor MB, and contact members I4! i the preferred circuit breaker P to the positive control bus. The energizaticn of relay l i l causes the right-hand actuating coil |l2 of relay 3 to be energized over a circuit which may be traced from the positive conrol bus, contact members |4| ci preferred breaker P, conductor |40, Contact members i4@ and ES! oi the relay conductor |156 and actuating coil |42 to the negative control bus.

The operation of relay I i3 establishes an energizing circuit for the transfer relay IIE which extends from the negative control bus through Contact members id'.' of relay HE, conductor |48, actuating coil of relay H5, conductor |49 and contact members 59 on relay H4 to the positive side of the control bus. No further operation takes place until the close switch I5 has been released at Which time actuating coil of relay III is dei-energized to permit the opening of the relay.

Relay I i! closes its contact members |53 when the close switch l5 is released, to establish a circuit for energizing the circuit closing relay 42 which may be traced from the positive side of the control bus, contact members S5! of the preferred circuit breaker P, actuating coil of Cir relay A2, conductor |52, contact members ISS, conductor 55, contact members 55 of the transfer relay ii, conductor Eet, contact members l? of relay conductor i533 and contact members 55 of the auxiliary circuit breaker A to the negative control bus. The closure of the preferred circuit breaker P will cause a negative potential to be applied to the control wire S ,3i in order to insure that a continuity of supply will be maintainedY on the main power bus. When the power supply fails on the preferred feeder circuit 35, the actuating relay t@ will be immediately cie-energized. A circuit will then be set up for Vtripping the preferred circuit breaker P which may be traced from the negative control bus, contact members itl of the preferred circuit breaker P, trip con 33, conductor AI 52, contact members i522, conductor 56, contact members E55, conductor ld, and contact members E52 of relay lit, to the positive control bus'.

At the same time a'circuit is set up for energizing the circuit breaker closing relay l5 which may be traced from the positive control bus, contact members i2@ of the auxiliary circuit breaker A, actuating coil of relay d5, conductor E39, contact members isi, conductor I3?, contact members i @3 of relay i i5, conductor les, contact members I of relay t, conductor E55 and contact members i of the preferred breaker P, to the negative control bus.

It will be Observed that the auxiliary circuit .breaker A is prevented from closing until thev preferred circuit breaker P has been opened and its Contact members 55, are closed.

lThe energization of relay 135 will cause the energization of the closing coil 'fili over an obvious circuit and the auxiliary circuit breaker A will then be closed.

When the power is again applied to the preferred feeder circuit 3G, the voltage delay relay 'il will be energized and a predetermined time there-Y after its contact members will be closed to ener gize the actuating relay 56. Y

When the actuating relay i5 closes, a circuit is set up for tripping the auxiliary ccuit breaker A which may be traced from the negative control bus through contact members ISB of the auxiliary circuit breaker A, trip coil 33, conductor v 30, contact members 36, conductor I32, contact members E63, conductor ilifcontact melA ers i575 of relay et, to the positive control bus.

The closure of contact members E59 of the auxiliary circuit breaker A energizes the closing relay lt-2 to eect the closure of the preferred circuit breaker P. The energizing circuitV forY relay ilmay be traced from the positive control bus, through contact members iftofY the preferred circuit breaker P, actuating coil of relay 52, contact members ISS, conductor E54, contact members'l, conductor I, contact members i5? of relay Alt, conductor Iiii and contact members i of the auxiliary circuit breaker A, tothe negative side of the control bus.

The corresponding operation indicators at the office will'be operated to indicate that the auxiliary circuit breaker A has opened .and that the preferred circuit breaker P has closed in the same manner as set forth hereinbefore.

In the event that it is desired to arrest the automatic operation of the system after the auxiliary circuit breaker A has beenclosed to prevent the preferred circuit breaker P from being automatically closed upon reapplication of power to the preferred Vfeeder 'circuit 36,*the automatic arresting relay llt is operated. o t

The circuit for energizing this relay H6 is established by the operator depressing a push button I il at the oiiice which applies positive potential through conductor 9 to the actuating relay I I5, thence through conductor It?, contact members ISB of relay I I5, conductor It, contact members I'ill of relay 46, conductor lll, contact members ilZof the auxiliary circuit breaker A, conductor H3 and contact members lii .on circuit breaker P to the negative control bus.

At the same time that the arresting relay H6 is energized, the main control relay H2 is `also energized on the application of Vpositive'potenti'al to the conductor 9 through the actuating coil of relay H2, conductor H8 and contact members |35 of the auxiliary circuit breaker A to the negative side of the control bus. Y

Operation of relay H2 establishes an energiz-l ing Vcircuit forY the right-hand coil IZB of relay IM which may be traced from the positive control bus, through contacts ile ofY relay BIE, conductor |22, contact members 23 and lZ, conductor IE5, and actuating coil |26 to the negative control bus. Contact members le!) of relay I I4 are thereby opened and transfer relay H5 is de-energized. The de-energization of relay H5 opens contact members I through whichthe energizing circuit for the actuating coil of relay l i6 was completed. However, the actuating coil of relay I lr6 is connected directly to the negative Vside of the control bus over a circuit which'eX- 'Ihe opening of Contact members 55e of relay` H4 and |41 on relay H3 due to the energization of relay IIS serves to insure that the transfer relay I l5 will be de-energized with the result that automatic transference of the system back to the preferred feeder circuit 3d is prevented on reapplication of power thereto.

When the operatorreleases the push button ll'l, relays I i2 and H6 willbe immediately deenergized. Y

It will now be observed that any action on the part of relay @5, when power is again applied to the preferred feeder circuit, will not initiate the automatic transfer back to the preferred feeder Vcircuit because relay H5 is de-energized.

In the event that it is desired to parallel the preferred feeder `circuit Se with the auxiliary feeder circuit 31 when the automatic transfer has F been arrested, as previously described, the operator depresses the close switch I5, that is associated with the preferred circuit breaker at the oice, thereby energizing relay Ill over a circuit which has been previously traced. The rightaccade? liand'coi'l |42 of relay IISisYthenenergized over a circuit which. may be traced from the positive control bus through contact membersl I4I ofthe preferred circuit breaker P, conductor IN,- contacty members IM and I9I, conductor H6` and relay coil |42V to the negative control bus. No further. action will take place until. the operator releascs'tlie close`switch I5 at which time relay I'I-.I will be de-energized.

A circuit will then be completed for actuating the circuit breaker relay 4Z which maybe traced fromA the positive control bus. through contact members |5.I of. the preferred circuit breaker P, actuating coil of relay 42', conductor |52; contact members |53, conductor |54, contact members |82` of relay II5, conductor |83, contact members Iofrelay I I6,.conductor |85, and contact memfbers |86, to the negative control bus The. preferred: circuit breaker P will. then be closed. and the'V corresponding operation indicationsent back to the'oflice as previously described.

When it is desired to again condition the sys-'- tem` for automatic operation, the operator de pressesthe trlpWswitch I6, associated-with the l' auxiliary circuit breaker,- thereby causing the gizedandthecircuits will be set upfor automatic transference fromv the preferred circuit to the auxiliary.` feeder circuit in the. event thatk power should fail on. the preferred. feeder circuit. In addition,..the circuits .will again be :set upfor'automatically transferring from'.v the. auxiliaryl feeder circuit back to the preferred feedercircuit when power'islreturned tothelatter circuit.

Since certainl further.l changesy may be made inthe above construction and: different embodimentsof the-invention. may. be made without departing. from the scopethereoit is .intended that all-matter contained in the above description. or shown in. the accompanying .drawings shall. be interpreted. as illustrative and not ina limiting Sense".

Weclaim: asrour invention:

I. In aI powerY control system, in combination, astation, a second station, a direct current control busl connecting the stations, circuit breakers atlV the second station for connecting a preferred. feeder circuit andi an auxiliary feeder circuitto amain power bus, control and'signallin'g means at'the'first station individualv toeach circuit breakerat the second'station, said'signalling means being responsive to different polarities, a control conductor forv connectingV each circuit breakerto the corresponding controll and signalling mean's at the first station, relay means responsive to the voltage applied to the preferred feedercircuit for transferring'th'e main power'bus from the preferred feeder circuit to the' auxiliary feeder circuit on failure of voltage oni the" former circuit and' for transferring the main power bus back to the preferred feeder circuit from the auxiliary feeder circuit on return of voltage to the preferred feeder circuit, control meansactuat'ed by the movementof. the circuit breakers for applying different polariti'es from the control bus tothe control conductors to actuate the signalling means for. indicating the positions of the circuit breakers,.locking.relay means at the secondstation. and` operable. from the. first station. over the control. conductor individuali to thev preferred fel' of the main power to the auxiliary feeder circuit by openingv thev energizing circuit to said transfer relay means when the preferred feeder circuit is trippedv5 from the first station, and a second locking relay'means at the second station and`I operablefroin the first station over the control'y conductorindividual tothe' auxiliaryl feeder circuit for preventing the' automatic transfer of tliefmain'powerbuseto the preferred feeder circuit by opening the `energizing circuit to said transfer relay" when theV auxiliary circuit breaker is closed froml the firststation.

2; In apower ccntfrolsystem, in combination, a main portier bus, preferred and auxiliary'feeder circuits, a pref red circuit breaker and an auxiliary circuit breaker for connecting the preferred and auxiliary' feeder circuits respectively to the main power bus, voltage-relay means responsive to the voltage applied to the preferred feeder circuit for opening the preferred circuit breaker and' closing the auxiliary circuit breaker on failure of voltageon the preferred feeder circuit and forop'ening theauxiliary circuit breaker and closing the preferred circuit breaker on return of vol'tagetov the preferred: feeder circuit, and' interlocking relay means connected to be energized on energization of the preferred feeder circuit forpreventing the-closure ofthe auxiliary circuit breaker prior tothe opening of the preferred circuit breaker when the interlocking relay` isk die-energized by maintaining the energizing circuit to the auxiliary circuit breaker open` and for preventing the closure of the preferred: circuit" breaker' prior toY the opening of the auxiliary circuit breaker when the interlocking relay is energized by maintaining the energizing circuit to the preferred circuit breaker open'.

3` In' a power control system, in combination, a first station, a. second station, a direct current control bus connecting the' stations, a preferred circuit breaker and an auxiliary circuit' breaker for. connecting a preferred feeder circuit and an auxiliary feeder circuit respectively to a main power bus, control" and' signalling means connected to the control bus at the first station and circuit on failure of voltage on the preferred feeder circuit' and`f'or transferring the main power bus back. to the preferred feeder circuit on return ofvoltage to said circuit, interlocking relay means connected to be energized' on energization of the preferred'feeder circuitffor preventing the closure of. the auxiliary circuit breaker prior to the opening of the preferred circuit breaker when the interlocking relay is de-energized by maintaining, the energizing, circuit to the auxiliary circuit breaker open and for preventing the closurev of the preferred circuit breaker prior to the. opening ofthe auxiliary circuitbreaker when the .inter-locking relay is. energized .by maintaining the energizing circuit tol the preferred circuit breaker open, and control means actuated by the movement of' the. circuit breakers for applying different polarities from the control bus to the control conductors to actuate the signalling means at the first station for indicating the positions of thecircult breakers.

4. In a power control system, in combination, aV first station, a second station, a direct current control bus connecting the stations, a preferred circuit breaker and an auxiliary circuit breaker for connecting a preferred feeder circuit and an auxiliary feeder circuit, respectively, to a main power bus, control and signalling means at the first station connected to the control bus and individual to each circuit breaker at the second station, said signalling means being responsive to different polarities, acontrol conductor for connecting each circuit breaker to the corresponding control and signalling means at'the rst station, a main control relay at the second station individual to each circuit breaker and disposed to beenergized over the control conductor on operation Yof the control means at the first station, a lockout relay at the second stationindividual to each. circuit breaker and disposed to /be energized on operation of the main control relay for setting upa closing circuit for its associated circuit breaker, said closing circuit being completed on de-energization of the main control relay, control means actuated by the movement of the circuit breakers for .applying different polarities from the control bus to the control conductors to actuate thesignalling means at the first station for indicating the positions of the circuit breakers, voltage relay means connected to be energized on energization of the preferred feedercircuit for opening the preferred circuit breaker and closing thel auxiliary circuit breaker on failure of voltage on the feeder circuit and for opening the auxiliary circuit breaker and Yclosing the preferred circuit breaker on return of voltage to the preferred feeder circuit, an automatic arresting relay at the second station for preventing the transfer of the main `power bus from the auxiliary feeder circuit to the pre- Y ferred feeder circuit by opening the energizing `ing relay.

5. In a power control system, in combination,

a first station, a second station, a direct current control bus connecting the stations, circuit breakers atthe second station for connecting a preferred feeder circuit and an auxiliarycfeeder circuit to a main power' bus, control and signalling means at the first station individual to eachA circuit breaker at the second station, said signalling means being responsive to different polarities, a control conductor for connecting each circuit breaker to the corresponding control and signalling means at the first station, relay means responsive to the voltage applied to the preferred feeder circuit for transferring the main power bus from the preferred feeder circuit to the auxiliary feeder circuit on failure of voltage on the former circuit and for transferring the main power busY back to the preferred feeder circuit from the auxiliary feeder circuit on return of voltage to the preferred feeder circuit, control means actuated by the movement of the circuit breakers for applying different polarities from the control bus to the control conductors to actuate the signalling means for indicating the positions of the circuit breakers, and locking relay means at vthe second station operable from the rst -station over the transfer'of themain power bus to the auxiliary feeder circuit` by opening the' energizing'circuit' to said transfer relay means when the preferred feeder circuit is opened from the first station: i

6. In a power control system, in combination, a first station, a second station, a direct current controlV bus connecting the stations, circuit breakers at the Asecond station ,for connecting a preferred feeder circuit and an auxiliary feeder` circuit to a main power bus, control and signalling means at the first station individual to'each circuit breaker at tbe second station, said signalling means being responsive to different polarities, a control conductor for' connecting eacli circuit breaker to the corresponding control and signalling means at the first station, relay means responsive to the voltage applied to the preferred feeder circuit for transferring thev main power bus from theV preferred feeder circuit to the auxiliary feeder circuit on failure of voltageon the former circuit and for transferring the main power bus back to the preferred feeder circuit from the vauxiliary feeder circuit on return of voltage to the preferred feeder circuit, control means actuated by the movement of the circuit ,breakersf for applying dierent polarities from the control bus to the control conductors to actuate thesignalling means for indicating the positions of the circuit breakers, andlocking relay means at the second station operable from the Vfirst station over the control conductor individu'al to the auxiliary feeder circuit for preventing tlie automatic transfer of th'e main power bus to the preferred feeder circuit by opening the energizing circuit to said transfer relay means when the auxiliary feeder circuit is closed fromthe firstV station.

7. In a power control system, in combination, a rst station, a second station, a direct current control bus connecting the stations, a preferred and an auxiliary circuit breaker at the second station for respectively connecting a preferred and an auxiliary feeder circuit to a main power bus, control means at the rst station individual to each circuit breaker at the second station, a control conductor connecting each circuit breaker to the corresponding control means at the first station, relay means responsive to the voltage applied to the preferred feeder circuit for transferring the main power bus from the preferred feeder circuit to the auxiliary feeder circuit on failure of voltage on the preferredfeeder circuit and for transferring the main power bus back to the preferred feeder circuit on return of voltage thereto, locking relay means at the second station operable from the first station over the the control conductor individual to the preferred feeder circuit for preventing the automatic transfer of the main power bus to the .auxiliary feeder-circuit by opening the energizing circuit to said transfer relay means when the preferred feeder circuit is opened from the first station, and a second locking relay means at the second station operable from the first station over the control conductor individual to the auxiliary feeder circuit for preventing theV automatic transfer of the main power bus to the preferred feeder circuit by opening the Venergizing circuit to said transfer relay means when the auxiliary circuit breaker is closed Yfrom the iirst station.

8. In a power control system, in combination, a rst station, a second station, a direct current control bus connecting the stations, a preferred and an auxiliary circuit breaker .at the second station for respectively connecting a preferred and an auxiliary feeder circuit to a main power bus, control means at the rst station individual to each circuit breaker at the second station, a control conductor connecting each circuit breaker to the corresponding control means at `the first station, relay means responsive to the voltage applied to the preferred vfeeder circuit for transferring the rnain power bus from the preferred feeder circuit to the auxiliary feeder circuit on failure of voltage on the preferred feeder circuit and for transferring the main power bus back to the preferred feeder circuit on return of voltage thereto, and locking relay means at the second station operable from rst the control conductor individual 'to the pr rred feeder circuit for preventing the automatic transfer of the main power bus tc the auxiliary ceder circuit by opening the energizing circuit to said transfer relay means when the preferred feeder circuit is opened from the first station.

9. In a power control system, in combination, a first station, a second station, a direct current control bus connecting the stations, a preferred and an auxiliary circuit breaker at the second station for respectively connecting a preferred and an auxiliary feeder circuit to a main power bus, control means at the first station individual to each circuit breaker at the second station, a control conductor connecting each circuit breaker to the corresponding control means at the first station, relay means responsive to the voltage applied to the preferred feeder circuit for transferring tne main power bus from the preferred feeder circuit to the auxiliary feeder circuit on failure of Voltage on the preferred feeder circuit and for transferring the main power bus back to the preferred feeder circuit on return of voltage thereto, and locking relay means at the second station operable from the first station over` the control conductor individual to the auxiliary feeder circuit for preventing the automatic transfer of the main power bus to the preferred feeder circuit by opening the energizing circuit to said transfer relay means when the auxiliary feeder circuit is closed from the first station.

STUART C. HENTON. MELVILLE B. RANKIN. 

